It is well known in the metal coating industry that there is a continuing need for coatings used for paint bonding and corrosion resistance. This is especially true where the metal is steel, aluminum, magnesium, aluminum alloys and zinc surfaced articles including galvanized iron or steel, where such coatings are required in order to protect the articles against deterioration.
In the past many such coatings have been suggested and used such as phosphate, zincate and anodized films but, in general, these coatings have left much to be desired because of various deficiencies including complex and often difficult operating procedures and high costs.
Chromate conversion coatings have been used with varying degrees of success. The effective protective ingredient in these coatings seems to be chromium in the hexavalent state. It has long been recognized that it would be desirable to coat metals with an organic film forming resinous composition which would not only be adherent to the metal but would also provide corrosion resistance. Unfortunately attempts to accomplish this result have not been very successful.